Provide convenience method for transaction

[rewinfrey]

At each level, ActionCoordinator, ActionUseCase and ActionTask, allow for a simple convenience method for indicating the logic should be wrapped in a transaction.

[knittingdev]

Does this include the idea of having a before_tasks and after_tasks? Because one of the things I could see being useful in this gem is the ability to allow the current ActionUseCase to define if it's tasks occur before or after it's own call/